Review your question, as the area is not indicated clearly, and diameter should be in m not m^2.
If the Cross-sectional Area is given than
Volume= Area*height= 62.5 m^3
But if the given area is Surface Area then,
Volume= (Area*Dia)*Dia/4= 225 m^3
Description shows it is a cylinder. In that case, volume is simply area x ht=25x2.5=62.5cum.
Area is 0.785d^2=0.785x36=28.26sq.m, which is different from the area given in question.
If diameter is correct then volume is 28.26x2.5=70.65cum.
is it cone or cylinder or anything else?
area means base area or surface area?
Edit your question.
What type of solid is it? Without that information, it will be very difficult (if not impossible) to provide valid help.
cylinder or cone?
area- 25 m2, dia- 6 m2, hight- 2.5m, volume ?
